6884: RTF reports broken on intl chars

Fix the problem by wrapping each char in an RTF {} group.
A bit inflating the text, but fixes the bug :-)

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/branches/maintenance/gramps34@22695 4ae1f11a-8b86-4847-b8af-ab372f36d1fd